This invention relates to post seal arrangements for lead acid batteries.
Sealing arrangements for lead acid batteries are well known in the prior art. Many of these designs rigidly fix a battery terminal post to the cover of the battery so as to seal the battery contents. Over the life of a lead acid battery, however, plate growth is experienced, particularly with positive lead plates, resulting in movement of the terminal post. As a result, stress is generated in the battery cover. Typically, the cover is formed of an acid-resistant thermoplastic, and cover failure has been noted resulting from plate growth. Such failure may curtail a lead acid battery""s life span.
Various approaches have been taken to accommodate plate growth, including allowing for movement of the terminal post relative to the battery cover. These arrangements still provide a seal and have been referred to as xe2x80x9cmoveablexe2x80x9d post seals. For example, moveable post seals have been developed, wherein a battery cover includes a flexible member (e.g., a bellows) that is connected to a terminal post bushing, such as in U.S. Pat. No. 4,455,356, which issued on Jun. 19, 1984 to Barrett, Jr.; U.S. Pat. No. 4,898,795, which issued Feb. 6, 1990 to Stocchiero; U.S. Pat. No. 5,053,296, which issued Oct. 1, 1991 to Stocchiero; U.S. Pat. No. 5,660,946, which issued Aug. 26, 1997 to Kump et al.; and, U.S. Pat. No. 6,312,852, which issued Nov. 6, 2001 to Wagner. With these designs, the flexible member flexes in response to outward movement of the terminal post, thereby avoiding stress build-up in the cover.
In an alternative approach, a terminal post is allowed to move freely within a surrounding sealing member, and/or has a sealing member mounted thereto which moves freely within a surrounding cooperating member, such as in U.S. Pat. No. 4,164,069, which issued Aug. 14, 1979 to Jensen; U.S. Pat. No. 4,212,934, which issued Jul. 15, 1980 to Salamon; U.S. Pat. No. 4,331,748, which issued May 25, 1982 to Hardigg, et al.; and, U.S. Pat. No. 4,495,260, which issued Jan. 22, 1985 to Hardigg, et al.
To overcome shortcomings of the prior art, a terminal post seal arrangement for lead acid batteries is provided herein which may be used both as a moveable post seal or as a static post seal. In a first aspect of the subject invention, a battery is provided having a cover with at least one aperture; a bushing formed to receive a terminal post of the battery disposed in registration with the aperture; and, a sealing member rigidly fixed to both the cover and bushing. The sealing member is preferably formed of different material from the cover, and more preferably, it is of an elastomeric material. The sealing member provides rigid (and hermetic) seals at both the cover and the bushing to prevent acid leakage from the battery. In addition, it is further preferred that the sealing member include a slack portion between its rigid connections which allows for relative movement between the bushing and the cover. Advantageously, the sealing member can allow for terminal post movement in response to plate growth without sacrificing seal integrity.
In a second aspect of the subject invention, a battery is provided having a cover with at least one aperture and a protruding collar that at least partially bounds the aperture. A bushing is also provided formed to receive a terminal post, with a sealing member being disposed between the bushing and the collar. The collar and/or sealing member are formed at least partially tapered such that relative movement between the collar and the sealing member causes interferent engagement. With such interferent engagement, a seal can be generated between the two elements. It is preferred that interference between the collar and the sealing member become greater with increasing extent of relative movement. Thus, the integrity of the seal generated between the two elements can increase with additional relative movement. With increasing plate growth, and corresponding terminal post movement, seal effectiveness about the terminal post may be increased over time.
These and other features of the subject invention will be better understood through a study of the following detailed description and accompanying drawings.